Phase generated carrier modulation and demodulation algorithm is one of the key technologies for interfering measurement. The principle of modulation and demodulation of phase generated carrier is elaborated, the best numerical values of relevant parameters are illustrated, the two traditional phase generated carrier algorithms are introduced, the problem of limited dynamic range, companion amplitude modulation, carrier phase delay and corresponding solutions are described. Finally, the problem related to phase generated carrier modulation and demodulation algorithm is summarized and the trend of optical fibre sensor is forecasted.

When detecting water vapour, the traditional tools have low spatio-temporal resolution. Lidar can improve the credibility of weather forecast. According to the theory of error analysis, the error sources of water vapour and their contributions are investigated based on the experimental data. Meanwhile, the computed relative errors are compared with that calculated relative errors from Raman lidar and radiosonde data. It turns out that the error sources on water vapour observed by Raman lidar includes the calibration constant, the transmission correction and the Raman scattering signals. The calibration constant error is about 4% and constant with height, and the major contribution to the total error under 1.5 km height. The transmission correction error increases slowly along with the height and less than 4% in the condition of clean air. The Raman scattering signals error is less than 20% under 3 km height, but it becomes the main source above 3 km height. The comparison shows that the relative error derived by Raman lidar agrees well with the calculated relative error. In summary, the analysis results above are helpful to promote the application of Raman lidar in weather forecast.

In the field measurement, different signal to noise ratios (SNR) have a great impact on the experimental results with the same instrument and data processing methods. By analyzing the noise model measured in the field, the same noise is added to the spot image simulated to change the SNR while the signal intensity is kept unchanged. When the SNR is less than 5, the relative deviation increased significantly. Then different methods are used to subtract the background noise under the same SNR, and it is found that the Gaussian noise has little effect on the centroid position after subtracting the average background value. The results show that the overall performance of the subtraction of 1 times average background and 0.6 times background fluctuation standard deviation is found to be the best.

Using POM02 solar photometer’s measured data in Delingha and Hefei, China, statistical analysis of atmospheric aerosol optical depth (AOD) and wavelength exponent was carried out in the two area from 2012 to 2014. Then the relationship was obtained between AOD change and wavelength all year round in Delingha and Hefei respectively. The change characteristics of monthly average aerosol depth was analyzed. The change characteristics was obtained such as wavelength exponent, turbidity coefficient, aerosol optical depth, and other parameters, which are significant in studying the aerosol optical properties in the two area.

Ammonia(NH3) generated from vehicles which is an important source of atmospheric PM2.5 can react with the acidic gases in the atmosphere to produce ammonium salt. To understand the emission of atmospheric NH3 in the traffic environment of Beijing City, China, and find the factors which affect the NH3 concentration of traffic environment and relationship between them, NH3 concentration at two observation sites was collected during the seven-month observatory experiment using DOAS instrument. One observation site was located in a typical traffic environment close to the eastern gate of Beihang University (BH), the other one was located on the top of the seven-floor building in a typical downtown environment (BMEMC). The analytical result showed that the emission of pollutants is generally low in summer and high in spring and autumn and the 24 h NH3 concentration at the BH site (25.19 μg /m3) was higher than that at the BMEMC site (15.90 μg /m3). The change trend of concentration in whole day is stable, and there are obvious peaks and troughs, which indicates that the contribution of traffic pollution sources to NH3 is stable. The correlation analysis indicated that NH3 concentration was well correlated with the concentrations of PM2.5, NO2, NOx and CO, but only weakly correlated with the concentrations of NO. It is concluded that the wind above Grade 3 is beneficial to the rapid diffusion and reduction of ammonia concentration. After calculating the yearly emissions and hourly emissions of all types of motor vehicles in Xueyuan Road, the result shows that NH3 mainly comes from small passenger cars (gasoline) and taxis (gasoline) (97.9%).

During the Spring Festival in 2016, PM2.5 and PM10 samples were collected from small particle sampler in Xi’an, China. The 30 effective samples were collected. The mass concentration characteristics and the distribution of the 16 polycyclic aromatic hydrocarbons (PAHs) were analyzed by high performance liquid chromatography (HPLC). The PAHs sources in PM2.5 and PM10 were analyzed by the ratio method and meteorological parameters. The results showed that the PM2.5 mass concentration was 180 μg·m－3 and PM10 was 286 μg·m－3. The concentration of PM2.5 was significantly higher than that of New Year’s Eve (PM2.5 average concentration was 160 μg·m－3, PM10 was 88 μg·m－3). PAHs are mainly distributed in PM2.5 fine particles, accounting for more than 70%. The ring numbers of aromatic distribution in PM2.5 and PM10 are mainly 3, 4 and 5. During the period, the PAHs high concentration continued to rise, it was mainly due to the incomplete combustion of heating coal in winter and the traffic pollution caused by gasoline and diesel vehicles. The sudden rise of PAHs concentration mainly came from the burning of fireworks.

The influence of the tilting angle of the circular optical path under the aperture angle on the modulation degree and the phase error is analyzed, and the dynamic calibration scheme is designed. Considering that the traditional proportional-integral-derivative (PID) controller is strictly dependent on the mathematical model of the dynamic correction system, while in the real closed-loop system, some parameters still can’t be accurately obtained. Fuzzy PID control strategy is used, and the fuzzy input and output of membership function is selected after the development of fuzzy rule base, fuzzy reasoning, the closed-loop corrected system is given. According to the experiment, the feasibility of the method is verified, which can effectively get rid of the dependence on the exact mathematical model of the calibration system. It can increases the laser interference modulation degree from 0.6 to 0.99, and the phase difference is reduced to 0.1°, the stability and adjustment time are also much better against the traditional PID controller.

In the project of on-orbit calibration, two apertures were designed with nominal diameters of 20 mm and 0.5 mm for switching observations of the earth and the scen, the high precision measurement of the two apertures area ratio is the key to ensure the calibration accuracy. The measurement method of the area of aperture was discussed briefly. Based on the measurements characteristics of the area of aperture, the ratio of the area of the two apertures to the area of the referenced aperture was measured by utilizing laser raster scanning and flux comparison. The area ratio of aperture Φ20 mm to Φ0.5 mm was 1604.381 with a total relative combined standard uncertainty 0.046%. The conclusion provides a feasible solution for the high-precision measurement of the aperture area ratio, and supports the on-orbit calibration of direct solar viewing.

An orbit temperature control system with high precision and stability is designed, which is aimed to satisfy the temperature requirements of satellite-borne multi-channel shortwave infrared detectors. First of all, according to the demand of operating temperature, the precision requirement of the shortwave infrared detector is presented. Then, the circuit, which acquires temperature with high stability as well as control thermal with low noise, is designed. Meanwhile, the pulse width modulation signal, established by FPGA based on the switch control algorithm, is used to control current of the thermoelectric refrigerator. The requirement of high stability temperature control with limited resources has been realized. The final test results show that the precision of the control system can reach ±0.1°, and meets the accuracy stability requirement of operating temperature.